I am not an expert, but I have tinkered with computers since the early 80s. Many problems are fixable.
If you already have AVG tune-up, that should work too.
Honestly, c4p, if you were a gamer etc or doing heavy-duty work (in terms of taxing the computer), I would say yes. But, it sounds like you are more like me in that you work hard on your computer with creating documents, email, surfing. In terms of taxing the computer, that's pretty low.
Unless you want to get a new PC, I wouldn't. Just back up your documents and other files like pix, music, etc, and then clean up your computer. I've had a lot of friends who have complained about similar issues with their PCs. If you use the tune-up software, it makes a big difference.
Sadly, in my experience, Windows degrades over time, and you have to maintain it. The AVG program or the others I have mentioned automate the maintenance. Similarly, browsers get bloated from websites you've visited, cookies, and other "junk", a lot of which slows your internet experience down. Similarly, you need to maintain these too.
The other thing is that the price of PCs has skyrocketed, as there is a massive chip shortage around the world.
Note that there have been some serious worldwide internet outages and other issues in the past few weeks. That might slow you down for internet related work, but it shouldn't affect your use of Word.
I honestly think you're better off cleaning up your PC and seeing how things work after that. Unless you REALLY want a new PC!